Optimization method for S characteristic of pump turbine

Abstract

The invention relates to the technical field of optimization methods of S characteristics, and discloses an optimization method of S characteristics of a pump turbine, which comprises the following steps: step 1, acquiring an S characteristic curve of a turbine runner; 2, a plurality of nozzles used for generating jet water are arranged on the top cover of a vaneless area between the movable guide vane and the rotating wheel; and step 3, opening the nozzle during operation in the S characteristic area. And the S characteristic is optimized, meanwhile, the flow disturbing effect on a blade-free area flow channel under the normal power generation and water pumping working conditions is avoided, and the hydraulic performance is effectively guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of optimization methods for S characteristics, and particularly to an optimization method for the S characteristics of a pump-turbine. Background Art

[0002] When the pump-turbine operates at a small flow rate in the power generation condition, the full characteristic curve presents an S shape, which is called the S characteristic of the pump-turbine. In this condition, in the "no-blade zone", that is, the cavity area between the runner and the movable guide vane, there is a "ring-shaped fluid" rotating at a high speed, which hinders the flow of water from the upstream side, that is, the guide vane area, towards the runner direction, resulting in a sharp drop in the flow rate through the turbine; when the flow rate in the turbine direction decreases to a certain extent, under the action of the strong centrifugal force of the runner blades, a large number of disordered water flow vortices appear between the runner blade channels, and the local water flow starts to flow in the reverse direction, forming a "partial reverse pump" flow phenomenon. As the reverse flow intensifies, the runner begins to enter the reverse water pumping state, that is, the reverse pump state. In this state, the inside of the pump-turbine is extremely unstable, which is likely to cause difficulties in unit grid connection or failure to reach no-load stability after load rejection, resulting in tripping. To improve the internal flow pattern of the runner in the "S" characteristic area of the pump-turbine and achieve stable grid connection in the "S" characteristic area of the unit.

[0003] Chinese patent document CN119312427A discloses an optimization method for the S characteristics of a pump-turbine, which is specifically carried out according to the following steps: Step 1, obtain the S characteristic curve of the turbine runner; Step 2, according to the magnitude of the mutation of the S characteristic curve, install N spoiler bars in the no-blade area between the movable guide vane and the runner; the spoiler bars are arranged on the pitch circle with a diameter of Dr, and the value range of Dr needs to satisfy D1 < Dr < D3; D1 is the outer diameter of the runner crown; D3 is the inscribed circle diameter of the tails of each movable guide vane when the opening of the movable guide vane is the largest, and D1, Dr, and D3 are concentric circles.

[0004] The existing technology improves the S characteristics of the pump-turbine through the spoiler bars. The water flow at the runner inlet collides with the spoiler bars, and the wake flow formed by the collision squeezes the inlet return vortex, making the shape of the inlet return vortex elongated and extending towards the center of the runner. Although it can improve the S characteristics of the pump-turbine under this specific condition, due to its existence, it will cause flow disturbance to the flow channel in the no-blade area during normal power generation and pumping conditions, destroy the flow field in this area, and affect the hydraulic performance. Summary of the Invention

[0005] In order to solve the technical problem that the spoiler bars destroy the flow field in this area and affect the hydraulic performance, the present invention provides an optimization method for the S characteristics of a pump-turbine, which is characterized by including the following steps: Step 1, obtain the S characteristic curve of the turbine runner; Step 2, arrange a plurality of nozzles for generating jet water on the top cover in the no-blade area between the movable guide vane and the runner; Step 3: When running in the S characteristic zone, turn on the nozzle.

[0006] In order to accurately, quickly and effectively eliminate the S-characteristic, the water pressure generated by the nozzle is greater than the maximum head pressure.

[0007] Preferably, the nozzles are periodically and symmetrically arranged in the circumferential direction of the bladeless area.

[0008] Preferably, the nozzles are arranged on a pitch circle with a diameter of Dr. The range of Dr values ​​must satisfy D1 < Dr < D3, where D1 is the outer diameter of the crown on the rotor, D3 is the inner diameter of the tail of each movable guide vane when the movable guide vane opening is at its maximum, and D1, Dr and D3 are concentric circles.

[0009] Preferably, the water pump turbine experiences significant hydraulic fluctuations during braking and reverse pumping operations, resulting in a reverse S-shaped guide vane opening line on the comprehensive characteristic curve. At this point, the nozzle is opened to inject high-pressure water.

[0010] The present invention has the following beneficial effects: 1. The present invention uses a high-pressure jet of water generated by a nozzle to cause a high-speed rotating "annular fluid" to collide with it, breaking the "annular fluid". The wake flow generated by the impact squeezes the return vortex at the runner inlet, forcing the vortex core to extend towards the central axis of the runner, significantly reducing the volume occupied by the return vortex at the runner inlet, thereby improving the flow efficiency and thus improving the S-characteristics of the water pump turbine.

[0011] 2. Precise Disturbance: The jet is activated only in the S-characteristic region (braking / reverse pumping conditions), avoiding continuous interference from traditional turbulence rods on the bladeless flow field in normal power generation / pumping conditions. Transient response advantages: The jet start-up and shutdown are synchronized with the switching of operating conditions, eliminating additional hydraulic losses caused by fixed turbulence structures (such as wake separation and turbulent kinetic energy dissipation caused by turbulence rods under normal operating conditions). It will not cause turbulence in the bladeless flow channel in normal power generation and pumping conditions, effectively ensuring hydraulic performance. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the nozzle installation of the present invention; Figure 2 for Figure 1 A schematic diagram of the cross-section of the nozzle installation area; Figure 3 This is a comprehensive characteristic curve graph. Detailed Implementation

[0013] The following detailed description illustrates the specific implementation method: The reference numerals in the accompanying drawings include: 1. movable guide vane; 2. blade; 3. nozzle; 4. top cover; 5. guide vane opening line; 6. S-characteristic operating zone.

[0014] Example 1 like Figure 1-3 As shown, a method for optimizing the S-characteristics of a water pump turbine includes the following steps: 1) Obtain the S-characteristic curve of the turbine runner; 2) Based on the magnitude of the abrupt change in the S-characteristic curve, several nozzles 3 for generating high-pressure jet water are periodically and symmetrically arranged on the top cover 4 of the bladeless area between the movable guide vane 1 and the impeller (the larger the abrupt change, the more nozzles are needed); the nozzles 3 are arranged on the pitch circle with a diameter of Dr, and the range of Dr must satisfy D1 < Dr < D3, where D1 is the outer diameter of the crown on the impeller, and D3 is the inner diameter of the tail of each movable guide vane 1 when the opening of the movable guide vane 1 is at its maximum. D1, Dr and D3 are concentric circles. 3) The pump-turbine experiences significant hydraulic fluctuations during braking and reverse pumping operations. On the comprehensive characteristic curve (Q11-n11 curve), the guide vane opening line 5 exhibits an inverted S-shape, which is the S-characteristic operating region 6. During operation in the S-characteristic region, the nozzle 3 is opened to inject high-pressure water (the water pressure generated by the nozzle 3 is greater than the maximum head pressure to ensure that the jet maintains its basic water column shape when entering the bladeless region), forming a water column. At this time, due to the presence of the high-pressure jet water column, the high-speed rotating "annular fluid" collides with it, thereby interrupting the "annular fluid" to a certain extent. Furthermore, the wake flow formed by the collision compresses the inlet return vortex of the runner, causing the shape of the inlet return vortex to elongate and extend towards the center of the runner, reducing the volume occupied by the inlet return vortex at the runner inlet. This can improve or suppress the inlet return vortex, enhance the flow capacity of the runner, and further improve the S-characteristics of the pump-turbine.

[0015] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for optimizing the S-characteristics of a water pump turbine, characterized in that, Includes the following steps: Step 1: Obtain the S-characteristic curve of the turbine runner; Step 2: Arrange several nozzles for generating jet water on the top cover of the bladeless area between the movable guide vane and the impeller; Step 3: When running in the S characteristic zone, turn on the nozzle.

2. The method for optimizing the S-characteristics of a water pump turbine according to claim 1, characterized in that: The water pressure generated by the nozzle is greater than the maximum head pressure.

3. The method for optimizing the S-characteristics of a water pump turbine according to claim 2, characterized in that: The nozzles are periodically and symmetrically arranged in the circumferential direction of the bladeless area.

4. The method for optimizing the S-characteristics of a water pump turbine according to claim 3, characterized in that: The nozzles are arranged on the pitch circle with a diameter of Dr. The range of Dr values ​​must satisfy D1 < Dr < D3, where D1 is the outer diameter of the crown on the rotor, D3 is the inner diameter of the tail of each movable guide vane when the movable guide vane opening is at its maximum, and D1, Dr and D3 are concentric circles.

5. The method for optimizing the S-characteristics of a water pump turbine according to claim 4, characterized in that: The water pump turbine experiences significant hydraulic fluctuations during braking and reverse pumping operations. The guide vane opening curve on the comprehensive characteristic curve shows an inverted S-shape. At this time, the nozzle is opened to inject high-pressure water.

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